AFM Conversion

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GeminiCoupe
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AFM Conversion

Post by GeminiCoupe »

We all know that air flow metres are no good when it comes to high performance apps you would go the aftermarket ECU/Map sensor route however real world states that thy should not overly modify daily driver when project sits there collecting dust...so here goes.

I remember reading a while back on the Gemini forums [of all places] about converting a Piazza to use a hotwire type AFM. Anyone know how/what/where to do this conversion? I think this particular conversion used an S13 SR20DET AFM and some wiring mods to get the computer to read it.

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Post by Bugle »

Yeah was just a guy that made his own equivalent of the Jaycar fuel adjuster. I bought a VL airflow meter for this but haven't got around to doing it. Gotta get the car back in one piece first.

Will have to wire in a resistor for the air temp sensor giving it a permanent temperature reading of maybe about 30 degrees? A hot wire AFM can measure the air mass no need for temperature.

Can do wiring into the original loom without chopping the AFM plug off by ripping the socket out of an R30 Skyline AFM at the wreckers and wiring that to the VL plug. I have the pinouts for the VL AFM somewhere hopefully I can find it.
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Post by rodavo »

Ive looked into doing this myself also. At the end of the day, when you do a bit of research, a hotwire airflow doesnt give much if any performance gain over a flapper style airflow meter. I dont think it is worth changing over if your using the standard computer. I have found however, that the standard airflow meter on my car was outputting around 3.2V at idle and got to the max of 5V quite early in the rev range. This was running 12 psi with everything else standard. So I think the next step for more performance is to tighten the spring on the airflow meter (I have heard that this can be done on the standard meter) and then look into the Jaycar Fuel Adjuster or something similar. I havent yet put my car on the dyno to look at the fuel mixtures, but I am planning too. Ive got a Jaycar Air/Fuel ratio meter hooked up at the moment and on 14psi it seems to be getting lean from around 5000 onwards which is scaring me a bit. I read on another forum that at 12psi, injector duty cycle reaches 100% so this might also be the explaination.

So many things to try out and test dont know where to begin!!! And I am in the process of upgrading the turbo as well!!!! Will it ever end!!! (I hope not) Ahhhh the joy of owning a piazza!!!

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Post by GeminiCoupe »

See the thing is, if your running the hotwire AFM you have to run the fuel adjuster, in a way this is an aftermarket computer as you can dial in more fuel when needed [to an extent]. I could be wrong, like i said im still fairly new to this subject. Much of my time has been devoted to finding the optimum EFI Turbo setup for a G series engine im building for the Gemini, so im new to the 4ZC1 and its workings.

Prob the biggest benifit for me is size. The old flap-type AFM is a big, nasty heavy sorta fucker and abit harder to find. The hotwire type is easy - go to pick a part and check out how many VL's and R31's are there and youll see what i mean. Makes it easier to plumb in a cooler and air filter setup.

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Post by Bugle »

True the VL one is much smaller and made from plastic so much lighter. It should flow more than the original because it's just a straight pipe with the wire suspended within, also there's a heat sink but the fins go in line with the air flow.
Inlet appears to have the same bolt pattern as the stock afm, and the outlet is the same diameter so it'll attach to the stock piping. It's just a bit shorter which may be a problem if you want to use the standard air box.
Got these pics
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Post by Bugle »

Another way fuel can be adjusted is by actually changing the fuel map in the ECU. I've had a look inside the Piazza ECU before but the microcontroller had JECS printed on it hiding the identity of the thing.
Yesterday at the wreckers thought i'd investigate what 80s Nissans were running. Had a look at an R31 Pintara CA20E and found the ECU to be nearly identical, made by JECS, similar part number to Piazza ECU, same sockets, same packages for the microcontroller and ROM. With those ECU's however they forgot to rebadge the things so I got the microcontroller part number which is a common 80s Microcontroller used in many things (Hitachi HD6301). So I should be able to dissassemble the code of the Piazza one if it's the same. Just gotta get another ECU don't wanna muck around with my only one..
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Post by shorty »

i found on a web site a little while back (can't remember what one it is now) that the piazza cpu dosen't run any maps, so as long as the injectors can keep up then it shouldn't lean out. also in the 4ze1 conversion that is located on the site somewere it says that the 4ze1 which is a 2.6 can run of the stock cpu and the guy also goes on to say that he upgraded injectors and ran 14 psi which would be possible if the cpu ran without a map in it. it would just adjust the pulse rate to keep the o2 at the reading it needs
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Post by Bugle »

Yeah that's what most people say because Holden claimed it to have Bosch L-Jetronic which is an analogue setup. It actually has an ECU made by Japanese Electronic Control Systems (JECS) and is definitely a digital microcomputer.

Oxygen sensor is only used in part throttle cruise conditions to keep the air/fuel ratio at 14.7:1. At full throttle the air/fuel ratio would go way off with different injectors.
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Post by Rodeobob »

On a similar subject,

Ive got a 2.6L and auto here that im going to fit into the KB20 ute.

Ive got the motor here, it came with a 89-90 ECM that runs the O2 sensor. Ive got the engine wiring but no harness and no plug for the computer.

The other day i grabbed the full loom (every wire in the car for everything) and ECM out of a 94 model. Its a different ECM with a different plug. All should be good as the engine harnesses have the same two plugs on both, i will double check but i do have the engine electrics off a 95 model just in case.

So ive got the motor stuff, ive got the loom and the ECM.
The only bit im missing is the AFM and the ducting to the TB.

The wrecker had an AFM and air box there but i didnt grab it, it was a square one and i wasnt sure if it was off a TF. It was a big flap type one. The TF Rodeo has an ugly round thing. I couldnt find any mounting brackets for a round one and he only had the bottom half.

Im a bit dumb when it comes to EFI shit.
Ive got two questions. nah make that three.
1. This ute is to be engineered, so if i fit up a different type AFM will it still be ok for emmisions etc as far as the engineer is concerned. Do all bits have to be standard??

2. What else could i use??? I rekon a VN-VS type commodore box would be a good one to use. What AFM do they use?? is it mounted to the box?? It would be mounted in a similar spot in the engine bay and the hole points in the right direction.
I could also use an N13 pulsar or LD astra one, they are metal and would paint up nice. Im sure i could fiddle with it to get it pointing right. These motors didnt run an AFM if i remember rightly.

3. The nissan type AFM, how would that wire in and interface with the Rodeo ECM???

It might be just easier to get a Rodeo AFM and air box.

Cheers. Bob.
Too many Piazzas to little money.

Currently unemployed. Watch this space.
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Post by Bugle »

You should use a standard AFM or else it could be sending the wrong signal to the ECU. One AFM may be outputting 4v while another may be outputting 3v for the same amount of air flow. You'd probably have to run a jaycar fuel adjuster if you were to use anything other than a standard one.

Most 80s AFM's seem to have the same bolt battern on the inlet so for an airbox to suit check over all the 80's Nissans, Toyotas and also VL Commodore.
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Post by GeminiCoupe »

So im under the impression here that the early 4ZE1's used a vein-type AFM like the Piazzas and the later models used the hotwire type? As for the questions..

rodeobob wrote:. This ute is to be engineered, so if i fit up a different type AFM will it still be ok for emmisions etc as far as the engineer is concerned. Do all bits have to be standard??
All bits are *supposed* to be standard. Speak with an engineer first and if they are satisfied that it wont change emissions you should be fine. Check if the later model engines ran the hotwire type AFM and use that as your arguement.

rodeobob wrote:What else could i use??? I rekon a VN-VS type commodore box would be a good one to use. What AFM do they use?? is it mounted to the box?? It would be mounted in a similar spot in the engine bay and the hole points in the right direction.
I could also use an N13 pulsar or LD astra one, they are metal and would paint up nice. Im sure i could fiddle with it to get it pointing right. These motors didnt run an AFM if i remember rightly.
Commodores ran a MAP sensor as did the Astra/Pulsar duo. Airbox will be useable though, just need to modify the lid/bottom half to match upto your AFM, which shouldnt be too hard. VL Commodore is a decent box to use, where the AFM mounts its on a 45deg angle so it should face towards the T/B. Would be perfect, especially if you are using a hotwire AFM.
rodeobob wrote:The nissan type AFM, how would that wire in and interface with the Rodeo ECM???
Not too sure on this one, although here goes. Im guessing it would be the same as trying to get it to go with the 4ZC1. Need to do something about the temp sensor on the ECU and maybe the fuel controller. Fuel controller would be illegal/unengineerable as it would wreak havoc with the emissions of the thing. Great for stopping the car leaning out up top on a budget, but frowned upon by the engineer.

Using the Rodeo AFM and airbox would probably be the best bet, atleast you know you wont have any hassles with the EPA. Im pretty sure ive got a spare 4ZC1 vein-type AFM coming with the Piazza [when i get around to getting picking the fucking thing up :shaking: ] so if you want in let me know.

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Post by Rodeobob »

Thanks guys.

The rodeos were vane type. This one was a 94 so that the later one without the exhaust O2 sensor.

I will have a look in the TF manual, it will be in there somewhere. it will have the test figures too.

I will grab the loom and see if it plugs into the piazza AFM. Its probably the same animal. Thats right ive even got a pod filter here that came on one of the piazzas, forgot about that. I need a piazza airbox for a piazza. lol.

Probably go with the std Rodeo gear. I will ring the wrecker and ask, hes probably got it in the shed, to easy to steal out of a car in the yard. Its the only country wrecker ive been to without a few nasty dogs in the yard.
Too many Piazzas to little money.

Currently unemployed. Watch this space.
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